Fortified wooden bowling pins



Nov. 27, 1962 w. R. EGBERT FORTIFIED WOODEN BOWLING PINS Filed Oct. 16, 1958 A v fwn! [Il Ill] l l... I

i lil l I l WILLIAM R. EGBERT Arrows-Ys:

United States Patent @nice Patented Nov. 27, 1962 This invention relates to new and useful improvements in fortified wooden bowling pins and similar wooden articles, whereby the resistance of the articles to impacts and wear and their service life are greatly enchanced.

The useful life of conventional wooden bowling pins, such as the larger bellied pins commonly referred to as ten pins and the smaller ones known as duck pins, is severely limited by the wear and tear of the wood which result from the direct impacts of bowling balls against the pins and from the crashing of pins one against another as the pins ily about in response to the impacts of the balls. l v

Various ways have been proposed for the purpose of increasing the wear resistance and service life of bowling pins. It has been proposed, for example, that the Wood at the belly of each pin be hardened by compression or be replaced by a layer of more durable material, so as to strengthen the pin at the points of impact by the ball.

The techniques heretofore proposed, however, have achieved little or no success in practice. They have left the pins still too suspectible to wear or failure to warrant their use, or have entailed excessive costs, or.have re-V quired objectionable departures from established standards of the games of bowling with respect to the size or the weight or the kinetic action` of the bowling pins.

The principal object of this invention is to provide' a new and improved fortified construction of wooden bowl ing pins which greatly enhances the wear resistance and service life of such pins anddoes so without entailing either excessive costs of production or departures from the` specifications established as official standards for the pins to be used in the games of ten pin and duck pin bowling.

I It has been found that there are two major zones of wear leading to pin failures in the use of conventional bowling pins. One of these zones, as commonly recognized, is located around the belly of each pin, where the wood takes most of the direct impacts of the bowling balls and of other pins. The second major wear zone is located around an inwardly tapered part of the base portion of the pin, near to the bellied portion but between it and the butt end of the pin. The wood at this inwardly tapered part suffers damage from impacts and wear as the pins l'ly about and strike one against another in response to the impacts of the bowling balls.

According to the present invention, bowling pins of the standard bellied forms are made by forming' each pin out of a unitary body of wood having an outer circumferential region of its bellied portion and also an outer circumferential region of a contiguous part of its base portion compressed and densified so that the wood in each of those regions possess a much greater density and hardness than the wood of the main body of the pin. Thus, an integral band of densified wood `highly resistant to wear and impacts is provided around each of the major wear zones of the pin. Bowling pins constructed with these densifed bands last several times longer in service than pins of conventional construction. Yet the depth and mass of the densiiied bands may beso limited relative to the total mass of each pin that the pins made according to this invention will conform fully with the established size, weight and performance specifications of standard bowling pins.

In carrying out this invention, there is first provided a wooden bowling pin blank that is oversized around its bellied portion and around an inwardly tapered part ofv its base portion located at the secondary wear zone of the ultimate pin. The wood in outer circumferential regions of those oversized parts is plasticized, such as by steaming it, or both steaming it and impregnating it with a resin forming substance, so as to soften the lignin and render wood fibres displaceable in those regions. .Then the regions of plasticized wood are each compressed circumferentially in a gradual manner, while heatf is applied, to bring about the required contraction-and densiiication of the plasticized wood. The blank thereafter is held in thecompressed form and cooled toharden the lignin and set the wood in a densiied state.

The densied wooden blank so obtained, upon being turned down and finished to the iinal dimensions-of th desired bowling pin, retains integral bands of highly wearresistant densied Wood throughout both of the major wear zones of the finished pin. These densiiied bands provided in pins made of the usual hard maple wood typically have a surface hardness ofV fromA 80 to'90.Shore durometer units, as vdetermined by tests with a Shore durometer, type D, produced by the Shore Instrument Manufacturing Company, of Jamaica, New York.. vThe surface hardness of the Wood of the main body of the pin ranges from as little as 60 to not more than about Shore durometer units.

Other features of the products provided by this .ini vention andthe constructionand operation of apparatus which I have provided for carrying out the invention will be apparent from the following description of illustrative embodiments thereof. The following description makes references to the accompanying drawing in which:

FIG. l is a schematic elevation of an oversized wooden blank suitable for conversion into a fortified bowling pin according to the invention; v v i FIG. 2 is a schematic elevation and quarter section of the same blank after having been compressed and densitied; l

FIG. 3 is a schematic elevation and quarter section of the finished bowling pin, the shade lines indicating the bands of densified wood;

FIG. 4 is a diagram illustrating successive steps in the method provided for converting each blank to a densifed form;

FIG. 5 is a perspective view of a collet provided for use in the compression of the blank; and

FIGS. 6 and 7 are schematic views of the collet, the blank and a coacting tapered passage of a tubular densiiication die in the beginning stage and the nal stage, respectively, ofthe compression of the blank.

The illustrations of the drawing relate particularly to the application of this invention for the production of bowling pins of the (A.B.C.) standard ten pin form, having the fortified construction described above. FIG- URES 1, 2 and 3 show typical forms of the wooden blank and the finished pin at successive stages of the production operations.

In FIG. 1, the form of a suitable roughly turned oversized wooden bowling pin blank is shown at A. The outline of the ultimate pin to be obtained from this blank is indicated by the broken line at C. The belly and a contiguous inwardly tapered part of the base portion of the blank are each made oversized as shown at 1a and 2a. The base portion continues to taper inwardly through part 2a to the bottom or butt end of the blank Vat 3a. A suitable belly diameter for the rough blank is one of approximately 53/16 inches.

For conformance with standard bowling pin specifications, the blank is made of hard maple wood with the grain of the wood running vertically, and the finished pin outlined at C is `brought to specified final dimensions including an overall length of 15 inches and a Igreatest belly diameter of approximately 4.775 inches, plus or minus 1,-{52 inch. That diameter may be somewhat smaller, to the extent of the thickness of any final coating or finish desired to be applied to the finished pin.

In FIG. 2 it is seen that after the conversion of the rough blank Ak to the densied form B, the upper part and the` butt of the blank may still have substantially thesame form as shown in FIG. l, but the bellied portion and the contiguous taperedpart of the base por-y to theiinal: pin dimensions, the resulting bowling pin has the form shown at C in FIG. 3. Only a small amount, of wood is removed from the densified bands in .the finishing operations, leaving the finished pin with a belly diameter 1c of approximately 4.775 inches. Thus the pin still has integral bands of densified wood extending to ar depth, for example, of aproximately 1/4 inch or more from its surfaces at 1c and 2c. These bands occupy zones of the pin surface extending from alocation not more than 3 inches above the plane of the finished bottom or butt 3c to a height of not less than 6 inches from that plane.

The upper band of densied wood lies substantially parallel tothe axis of the pin and spans the summit of the bellied portion, while the lower band lies at anangle to the axis and contiguous to the upper band, entirely in the tapered portion below the latter, and is composed of a pluralityfof frusto-conical sectors of densified wood disposed circumferentially of the pin with their ends in contiguous relation. The densified wood of each band is composed essentialy of tightly compacted displaced fibres and lignin of the natural wood still integrally united with the natural fibres and lignin of the contiguous undensified wood of the pin.

The conversion of oversized blanks such as those of FIG. 1 into the densified form of FIG. 2 is brought about by means of the methods and apparatus diagrammatically illustrated in FIGS. 4 to 7 of the drawing.

In the -first step of the conversion, the wood in outer circumferential regions of the bellied portion 1a and the tapered part 2a is subjected to a plasticizing treatment to soften the lignin and render the wood fibres displaceable in those regions. There are various known ways of effecting such a plasticization of natural wood.

In the method which I have found most effective for the purposes of this invention, the blanks are passed first into a steaming chamber, such as diagrammed at l() in FIG. 4, where the oversized portions to be densified are exposed to the action of steam until the moisture and heat of the steam have penetrated the wood to the depth desired for the densification. A steaming period of l5 to 20 minutes is usually suicient when introducing live steam into the chamber at a steam line temperature of 275 to 300 F.

While sheaming alone is effective to plasticize the wood, it is further advantageous to impregnate the wood with a chemical substance, such as a urea, that will form a resin in the plasticized regions of the wood in the course of the densiiication process. This enhances the dimensional stability and the durability of the product. For this purpose the steamed oversized regions of the blanks may be contacted with an alkaline aqueous solution of urea or dimethylolurea, or of both. A suitable solution, for example, is one containing, by weight, 8 parts of NaOH, 52 parts of borax, 384 parts of dimethylolurea and 340 parts of urea in 216 parts of water. If desired, the steamed blanks may be immersed in such a solution. I have found, however, that it is feasible and advantageous to effect the impregnation by spraying such a solution into the hot atmosphere of the chamber in which the steaming of the blanks takes place. For example, the steam chamber may be provided with a steam inlet as diagrammed at 11 and also with a Spayer 12 insiderthe chamber to which a solution of the resin forming substance is fed through pipe 13.

After the oversized regions of each blank have been plasticized to the desired depth, the blank while in a heated and moistvcondition is moved directly to, and treated in, a densificationV apparatus of the character illustratedat the right-hand side of FIG. 4 of the drawing. The main components of this apparatus are an elongated tubular densification die 20, a collet 30 which clasps and serves to compress the tapered part 2a of each blank, and a fluid pressure plunger system 40 which serves to force the blank and a clasping collet together through the tubular die.

The densification die 20 is formed by an elongated tube of heavy metal strong enough to withstand the very high pressures applied in the compression operation. At its inletend it forms a tapered or frusto-conical passage21 which extends, for example, for a distance of approximately 8 inches from the mouth 22 of the tube with its diameter progressively diminishing to a final diameter at 24 that is desired for the densitied band 1b at the belly of the Wooden blank, i.e., to nearly the final belly diameter of the finished bowling pin. The inlet end of the die tube 20 is heated, for example, by means of electrical resistance elements 23 surrounding that end for a distance of as much as 12 inches from the mouth 22. The heat from these elements is conducted through the metal Wall of the tube and thence to the oversized regions of the blank as they are compressed.

The long passa-ge 25 of the die tube 20, Which extends from the end of the tapered passage to the tube outlet` at 26, has a substantially uniform diameter that is substantially the same as the smallest or final diameter of the tapered passage. For a distance of as much as l2 inches from outlet 26, the outlet end of the tube is jacketed by suitable cooling means, such as by cooling coils 27 which are wound upon and carry a circulating cooling fluid in direct heat exchange with the tube.

The collet 30 in the form shown serves several functions in the course of the conversion of the plasticized blanks. Its principal function is to bring about the compression and densification of the oversized tapered part 2a of the blank. It performs this function through the coaction of a plurality of rigid compression elements 32 with that tapered part and with the tapered passage 21 of the densitication die. Its further functions include the locating and holding of the blank in proper relation to the die passage and to the compression elements 32' and to the plunger 44 of the lluid pressure system, vand the proper transporting of the blank and the compression elements 32 together through the die in response to the thrust of the plunger.

A suitable construction of the collet to achieve those functions is shown in the perspective View of FIG. 5. A rigid base plate 34 of heavy metal is provided to support and transport the blank, to support arms 3-1 which carry the compression elements 32 at their free ends, and to be centered on and take the thrust of the plunger 44. The plate 34 -is made of a size that will pass freely through the die passages 21 and 25. A socket 35 is provided in its backward side to fit over a centering pin 45 on the end of the plunger 44'and thus hold the collet in proper centered relation to the die passage.

A recess or cup 36 on the forward side of the base plate 34 receives the butt 3a of the blank and supports it in centered relation to the die passage. At spaced points around its periphery the base plate is notched or cut away as shown at 37 to receive the lower ends of the arms 31, each of which is pivoted to the plate by a strong pivot pin inserted at 38. Suitable spring means, for example, coiled springs 39 interconnecting the adjacent arms, are provided to bias the arms 31 toward one another and thus clamp the several compression elements 32 against the tapered part 2a of a blank received in the cup 36.

The compression elements themselves as here shown are formed as incompressible, relatively movable elements integral with the free ends of the supporting Iarms' 31. These elements are made of a heat conductive metal, for example, of a hard copper alloy, such as a brass, that readily transmits heat between the walls of the die passages and the clasped region of the blank.

Each element 32 has a tapered arcuate (frusto-conical) inner surface 32a of approximately the nal shape desired for a sector of the tapered densied band 2c of the finished bowling pin. Each element 32 also has an arcuate outer surface 32b shaped to bear -against and be slid along the inside of the dieV passages in direct heat exchange therewith. The several elements together are adapted to clasp the oversized tapered part 2a of the blank in nearly encircling relation thereto. Each of them has a wedge-like cross section terminating ina thin leading edge that lies between the blank and the wall of the tubular die, just below the bellied portion of the blank, as the collet with a blank therein is moved into and through the die.

The plunger system 40 comprises a uid pressure cylinder 42 mounted in ixed axial alignment with the die tube 20 and connectible with a source of -a suitable pressure uid to bring about the required movements of plunger 44. A hydraulic pressure fluid such as oil or water is preferably used for optimum control of the rate of movement of the plunger. The rate is regulated so that each plasticized blank will be forced gradu-ally through the tapered passage of the die tube at a low speed, for example, at a speed of the order of one inch per minute.

When the plunger is retracted into cylinder 42 its end is spaced far enough away from the mouth of tube 20 to enable the positioning of a plasticized blank A clasped in a collet 30 on the end pin 45 in alignment with the mouth tion, i.e., to a position as illustrated in FIG. 6 of the drawings. The plunger then is continued in gradual movement to force the blank and clasping collet slowly through the taperedpassage to a position in passage A25 beyond the end 24 of the taper.

In the course of that gradual movement, as indicated by FIG. 6 and FIG. 7, the plasticized wood in the oversized bellied portion la is heated, compressed and densiied by direct compression of that part of the blank against the heated tapered die wall. At the same time, `a band of the plasticized wood of the tapered part 2a is similarly heated, compressed and densied by the action of the compression elements 32 which transmit heat to the wood from the heated die wall and are gradually contracted forcibly against the wood as the blank and collet are forced along the tapered passage.

The blank carried on the end of the plunger is thus formed, before the end of the plunger stroke, with densified bands 1b and 2b having the desired dimensions and depths of compression. The plunger stroke leaves this blank in an intermediate part of the die where it is held in the compressed condition by the Wall of the straight tubular passage 25. A dwell of the blank at this point, While it is still in a heated and plasticized condition, contributes to the desired re-grasping of the displaced wood bers by the lignin in the compressed regions of the wood.

The plunger 44 is now retracted from the die, leaving the compressed blank and collet to dwell in passage 25, and another collet 30 clasping another plasticized blank A is positioned on the plunger and forced into Iand gradually through the tapered passage in the manner described above. As this next blank is being compressed, its head 4 engages the base plate 34 of the compressed assembly in passage 35 and gradually forces that assembly forward into the cooled end of the die. At that location, the compressed bands of the blank are cooled by flow of heat to the cold die wall at 27, and the Wood becomes permanently set in the densied state.

Upon a third stroke of the plunger to compress a third blank in the tapered passage 21, the die 20 at tirst contains three assemblies of blanks and clasping collets, in progressive stages of conversion. As the third stroke con# tinues the assembly in the cooling end of the die is soon forced out of the die outlet at 26, whereupon the collet is removed from the dens'iiied blank for re-use With another rough blank. The densilied blank is then obtained in the form hereinbefore described and shown at B in FIG. 2.

ln practical operations of the described method and apparatus, densiiied wooden bowling pins of the desired construction may be produced by use of a single die at the rate of 3 to 4 pins per hour. It will be understood that the production of pins may be carried on at any desired rate by the provision of a suitable number of production units.

While I have illustrated and described this invention with references to numerous details of the construction and the operation of illustrative embodiments, it is to be understood that the new features of this invention may be utilized in various other ways. They are not restricted to the illustrative embodiments except as may be required by a fair construction of the terms of the appended claims which are intended to define the invention.

I claim:

l. A wooden bowling pin comprising a unitary body of wood consisting essentially of the integrated fibres and lignin of a piece of natural wood formed to the configura tion of such pin, said body having a circumferential bellied portion and a base portion that diminishes in diameter toward the butt of the pin, said bellied portion and a contiguous part of said base portion each comprising an integral circumferential band of said wood that is compressed and densitied and possesses a substantially greater density and hardness than the bulk of the wood of said body, one of said bands lying substantially parallel to the axis of the pin and spanning theA summit of said bellied portion, the other of said bands lying in its entirety at an angle to said axis and being contiguous to said one band and being composed of a plurality of frusto-conical sectors of densified wood having their ends in contiguous relation, the wood of each of said bands being composed essentially of tightly compacted displaced fibres and lignin of the natural wood still integrally united with natural fibres and lignin of the substantially undensied wood of said body.

2. A wooden bowling pin comprising a unitary body of wood consisting essentially of the integrated fibres and lignin of a piece of natural wood formed to the conguration of such pin, said body having a circumferential bellied portion and a base portion that diminishes in diameter toward the butt of the pin, said bellied portion and a contiguous part of said base portion each comprising an integral circumferential band of said wood that is compressed and densified and possesses a substantially greater density and hardness than the bulk of the wood of said body, one of said bands lying substantially parallel to the axis of the pin and spanning the summit of said bellied portion, the other of said bands lying in its entirety at an angle to said axis and being contiguous to said one band and being composed of a plurality of frusto-conical sectors of densifed wood having their ends in contiguous relation, the wood of each of said bands being composed essentially of tightly compacted displaced fibres and lignin of the natural wood still integrally united with natural fibres and lignin of the substantially undensied wood of said body, saidfbands of densified wood having a surface hardness ofv approximately 80 to 90 Shore durometer units and the hardness of the bulk of the wood of said body being about 60 to 75 Shore durometer units.

3. A wooden bowling pin of standard ten pin form, comprising a unitary body of wood consisting essentially of the integrated fibres and lignin of a piece of hard maple wood formed to the configuration of such pin, said body having a height of approximately 15 inches, a bellied portion approximately 4.775 inches in diameter at its apex and a base portion that diminishes in diameter toward the butt of the pin, said bellied portion and a contiguous part of said base portion each comprising an integral circumferential band of said wood that is compressed and densied to a depth of approximately 1A inch from the surface thereof and possesses a substantially greater density and hardness than the bulk of the Wood of said body, one of said bands lying substantially parallel to the axis of the pin and spanning the summit of said bellied portion, the other of said bands lying in its entirety at an angle to said axis and being contiguous to said one band and being composed of a plurality of frusto-conical sectors of densifed wood having their ends in contiguous relation, the wood of each of said bands being composed essentially of tightly compacted vdisplaced fibres and lignin of the natural wood still integrally united with natural bres and lignin of the substantially undensied wood of said body, said compressed bands extending from a location not greater than approximately 3 inches from said butt to a location not less than approximately 6 inches from said butt, the weight of said pin being not in excess of 3 pounds and 10 ounces.

4. A wooden bowling pin of standard ten pin form, comprising a unitary body of wood consisting essentially of the integrated fibres and lignin of a piece of hard maple Wood formed to the conguration of such pin, said body having a height of approximately 15 inches, a bellied portion approximately 4.775 inches in diameter at its apex and a base portion that diminishes in diameter toward the butt of the pin, said bellied portion and a contiguous part of said base portion each comprising an integral circumferential band of said wood that is compressed and densified and possesses a substantially greater density and hardness than the bulk of the wood ofV said body, one of said bands lying substantially parallel to the axis of the pin and spanning the Summit of said bellied portion, the other of said bands lying in its entirety at an angle to said axis and being contiguous to said one band and being composed of a plurality of frusto-conical sectors of densified wood having their ends in contiguous relation, the wood'of each of said bands being composed essentially of tightly compacted displaced fibres and lignin of the natural wood still integrally united with natural fibres and lignin of the substantially'undensified wood of said body, said compressed bands extending from a location not greater than approximately 3 inches from said butt to a location not less than approximately 6 inches from said butt, the Weigh-t of said pin being not in excess of 3 pounds and 10 ounces, said bands of densied wood having a surface hardness of approximately 8O to 90 Shore durometer units.

References Cited in the file of this patent UNITED STATES PATENTS 1,068,775 Hyatt July 29, 1913 2,309,532 Phillips Jan. 26, 1943 2,562,807 McKenzie July 31, 1951 2,634,774 Francar Apr. 14, 1953 2,652,081 Curtis Sept. l5, 1953 2,654.606 Stearns et al. Oct. 6, 1953 

